GNU bug report logs - #17236
undo-only hangs when nils double up

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
To: emacs bugs <bug-gnu-emacs <at> gnu.org>
Subject: undo-only hangs when nils double up
Date: Thu, 10 Apr 2014 12:15:53 -0400

When there are consecutive nils in buffer-undo-list, undo-only can
hang. For example, if buffer-undo-list begins with (nil nil ...), then
the first undo-only succeeds, changes nothing, and inserts an identity
mapping into undo-equiv-table. The second undo-only hangs because the
identity mapping causes an infinite recursive lookup in
undo-equiv-table.

Perhaps the bug is in the Emacs package (Evil in this case) that
doubles up the nils. I ask here because the undo code already seems to
try to account for these to some extent. eg there are a few of these
in the undo function:

  (while (eq (car list) nil)
         (setq list (cdr list)))

Is this an Emacs bug or an Evil bug?

Message #8 received at 17236 <at> debbugs.gnu.org (full text, mbox):

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 17236 <at> debbugs.gnu.org
Subject: Re: bug#17236: undo-only hangs when nils double up
Date: Thu, 10 Apr 2014 19:23:10 +0200

Barry OReilly <gundaetiapo <at> gmail.com> writes:

> When there are consecutive nils in buffer-undo-list, undo-only can
> hang.

undo-boundary never creates such an entry.

Andreas.

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Message #11 received at 17236 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 17236 <at> debbugs.gnu.org
Subject: Re: bug#17236: undo-only hangs when nils double up
Date: Thu, 10 Apr 2014 16:30:21 -0400

> Is this an Emacs bug or an Evil bug?

Putting a double nil in the undo-list is an error, so Evil is to blame.
But that doesn't excuse the inf-loop.  We should check with `eq' that we
don't add an identity mapping to undo-equiv-table.


        Stefan

Message #16 received at 17236-done <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 17236-done <at> debbugs.gnu.org
Subject: Re: bug#17236: undo-only hangs when nils double up
Date: Sat, 12 Apr 2014 15:24:59 -0400

[Message part 1 (text/plain, inline)]

Rev 116951. The Evil bug was also reported and fixed.

[Message part 2 (text/html, inline)]

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